stat-util: add new macros for declaring statx variable

Let's deal with the msan initialization issue once for all cases instead
of over and over again.

src/basic/xattr-util.c

@@ -12,6 +12,7 @@
 #include "macro.h"
 #include "missing_syscall.h"
 #include "sparse-endian.h"
+#include "stat-util.h"
 #include "stdio-util.h"
 #include "string-util.h"
 #include "time-util.h"
@@ -154,12 +155,7 @@ static int parse_crtime(le64_t le, usec_t *usec) {
 }
 
 int fd_getcrtime_at(int dirfd, const char *name, usec_t *ret, int flags) {
-        struct_statx sx
-#if HAS_FEATURE_MEMORY_SANITIZER
-                = {}
-#  warning "Explicitly initializing struct statx, to work around msan limitation. Please remove as soon as msan has been updated to not require this."
-#endif
-                ;
+        STRUCT_STATX_DEFINE(sx);
         usec_t a, b;
         le64_t le;
         size_t n;